| 1. |
- Spiro, S., et al.
(författare)
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Low luminosity Type II supernovae - II. Pointing towards moderate mass precursors
- 2014
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 439:3, s. 2873-2892
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Tidskriftsartikel (refereegranskat)abstract
- We present new data for five underluminous Type II-plateau supernovae (SNe IIP), namely SN 1999gn, SN 2002gd, SN 2003Z, SN 2004eg and SN 2006ov. This new sample of low-luminosity SNe IIP (LL SNe IIP) is analysed together with similar objects studied in the past. All of them show a flat light-curve plateau lasting about 100 d, an underluminous late-time exponential tail, intrinsic colours that are unusually red, and spectra showing prominent and narrow P Cygni lines. A velocity of the ejected material below 10(3) km s(-1) is inferred from measurements at the end of the plateau. The Ni-56 masses ejected in the explosion are very small (< 10(-2) M-circle dot). We investigate the correlations among Ni-56 mass, expansion velocity of the ejecta and absolute magnitude in the middle of the plateau, confirming the main findings of Hamuy, according to which events showing brighter plateau and larger expansion velocities are expected to produce more Ni-56. We propose that these faint objects represent the LL tail of a continuous distribution in parameters space of SNe IIP. The physical properties of the progenitors at the explosion are estimated through the hydrodynamical modelling of the observables for two representative events of this class, namely SN 2005cs and SN 2008in. We find that the majority of LL SNe IIP, and quite possibly all, originate in the core collapse of intermediate-mass stars, in the mass range 10-15 M-circle dot.
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| 2. |
- Constance, B., et al.
(författare)
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Experimental Verification of the CLIC Two-Beam Acceleration Technology in CTF3
- 2013
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Ingår i: IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference. - 9783954501229 ; , s. 1436-1438
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Konferensbidrag (refereegranskat)abstract
- The Compact Linear Collider international collaboration is pursuing an extensive R&D program towards a multi- TeV electron-positron collider. In particular, the development of two-beam acceleration technology is the focus of the CLIC test facility CTF3. In this paper we summarise the most recent results obtained at CTF3: The results of the studies on the drive beam generation are presented, the achieved two beam acceleration performance is reported and the measured breakdown rates and related observations are summarised. The stability of the deceleration process performed over 12 subsequent modules and a comparison of the obtained results with the theoretical expectations are discussed. We also outline the future experimental program.
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| 3. |
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| 4. |
- Dabrowski, A. E., et al.
(författare)
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Measuring the bunch frequency multiplication at CTF3
- 2010
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Konferensbidrag (refereegranskat)abstract
- The CTF3 facility is being built and commissioned by an international collaboration in order to test the feasibility of the proposed CLIC drive beam generation scheme. Central to this scheme is the use of RF deflectors to inject bunches into a Delay Loop and a Combiner Ring, in order to transform the initial bunch spacing of 1.5 GHz from the linac to a final bunch spacing of 12 GHz. The optimization procedure relies on several steps. The active length of each ring is carefully adjusted to within a few millimeters accuracy using a two‐period undulator. The transverse optics of the machine must be set-up in a way so as to ensure the beam isochronicity. Diagnostics based on optical streak cameras and RF power measurements have been designed to measure the longitudinal behaviour of the beam during the combination. This paper presents their performance and highlights recent measurements.
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| 5. |
- Dabrowski, A. E., et al.
(författare)
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Measuring the bunch frequency multiplication at the 3rd CLIC Test Facility
- 2012
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Ingår i: Journal of Instrumentation. - 1748-0221 .- 1748-0221. ; 7, s. P01005-
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Tidskriftsartikel (refereegranskat)abstract
- The CLIC Test Facility 3 (CTF3) is being built and commissioned by an international collaboration to test the feasibility of the proposed Compact Linear Collider (CLIC) drive beam generation scheme. Central to this scheme is the use of RF deflectors to inject bunches into a delay loop and a combiner ring, in order to transform the initial bunch frequency of 1.5 GHz from the linac to a final bunch frequency of 12 GHz. To do so, the machine's transverse optics must be tuned to ensure beam isochronicity and each ring's length can finally be adjusted with wiggler magnets to a sub millimeter path length accuracy. Diagnostics based on optical streak camera and RF power measurements, in particular frequency bands, have been designed to measure the longitudinal behaviour of the beam during the combination. This paper presents the diagnostics and recent commissioning measurements.
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| 6. |
- Farabolini, W., et al.
(författare)
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Recent Results from CTF3 Two Beam Test Stand
- 2014
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Ingår i: Proceedings, 5th International Particle Accelerator Conference (IPAC 2014).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Adli, E., et al.
(författare)
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X-band rf power production and deceleration in the two-beam test stand of the Compact Linear Collider test facility
- 2011
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Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 14:8, s. 081001-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss X-band rf power production and deceleration in the two-beam test stand of the CLIC test facility at CERN. The rf power is extracted from an electron drive beam by a specially designed power extraction structure. In order to test the structures at high-power levels, part of the generated power is recirculated to an input port, thus allowing for increased deceleration and power levels within the structure. The degree of recirculation is controlled by a splitter and phase shifter. We present a model that describes the system and validate it with measurements over a wide range of parameters. Moreover, by correlating rf power measurements with the energy lost by the electron beam, as measured in a spectrometer placed after the power extraction structure, we are able to identify system parameters, including the form factor of the electron beam. The quality of the agreement between model and reality gives us confidence to extrapolate the results found in the present test facility towards the parameter regime of CLIC.
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| 8. |
- Hegner, E., et al.
(författare)
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Mineral Ages and P-T Conditions of Late Paleozoic High-Pressure Eclogite and Provenance of M Lange Sediments from Atbashi in the South Tianshan Orogen of Kyrgyzstan
- 2010
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Ingår i: American Journal of Science. - 0002-9599. ; 310:9, s. 916-950
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Tidskriftsartikel (refereegranskat)abstract
- Ages derived from various isotope systems in high-pressure (HP) rocks of the western Tianshan orogen of NW China have been interpreted as evidence for late Carboniferous and/or Triassic collision of the accretionary margin of the Central Asian Orogenic Belt (CAOB) with the Tarim Craton. In order to elucidate this controversy, we present new P-T data as well as Sm-Nd and (40)Ar/(39)Ar cooling ages for an eclogite sample from Atbashi in the accretionary m lange of the South Tianshan suture in Kyrgyzstan, some 500 km along strike to the west of the controversial locality in the upper Akeyazhi River Valley in NW China. A clockwise P-T path for the eclogite with peak pressures of 18 to 24 kbar at 520 to 600 degrees C is consistent with near-isothermal decompression and exhumation in a subduction zone before collision of the CAOB with the Tarim Craton. Geochemical data and an initial epsilon Nd value of similar to +9 suggest an N-MORB protolith for the eclogite. The high-pressure mineral assemblage of the eclogite yielded a statistically robust Sm-Nd isochron age of 319 +/- 4 Ma (2 sigma, 5 data points, MSWD = 0.4) for equilibration and closure of the Sm-Nd system during HP metamorphism. (40)Ar/(39)Ar dating of phengite from the same sample yielded a cooling age of 316 +/- 3 Ma (2 sigma) implying rapid exhumation. Docking of the Tarim Craton with the southern margin of the Middle Tianshan-North Tianshan blocks in Kyrgyzstan during the late Carboniferous is supported by widespread emplacement of A-type granitoids of early Permian age that suggest a setting of consolidated crust. An tuunetamorphosed and little deformed molasse-type conglomerate of latest Carboniferous age, overlying the HP rocks, indicates that HP metamorphism, exhumation, and exposure of the HP m lange occurred from 320 to 300 Ma. The detrital zircon age spectrum of a metagraywacke sample from the accretionary melange suggests sources in the Tarim Craton and/or from the Middle and North Tianshan that possibly comprise rifted blocks from Tarim.
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| 9. |
- Olvegård, Maja, et al.
(författare)
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High intensity profile monitor for time resolved spectrometry at the CLIC Test Facility 3
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 683, s. 29-39
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Tidskriftsartikel (refereegranskat)abstract
- The power source of the Compact Linear Collider (CLIC) relies on the generation and deceleration of a high-intensity electron drive beam. In order to provide the best radio-frequency (RF) to beam-energy transfer efficiency, the electron beam is accelerated using fully loaded RF cavities, which leads to strong beam loading effects resulting in a high-energy transient. The stability of the RF power produced by the drive beam depends on the stability of the drive beam energy and energy spread along the pulse. The control and the monitoring of the time evolution of the beam energy distribution are therefore crucial for the accelerator performance. For this purpose segmented beam dumps, which are simple and robust devices, have been designed and installed at the CLIC Test Facility 3 (CTF3). These devices are located at the end of spectrometer lines and provide horizontal beam profiles with a time resolution better than 10 ns. The segmented dumps are composed of parallel, vertical, metallic plates, and are based on the same principle as a Faraday cup: the impinging beam current is read by a fast acquisition channel. Both FLUKA and Geant4 simulations were performed to define the optimum detector geometry for beam energies ranging from 5 MeV to 150 MeV. This paper presents a detailed description of the different steps of the design: the optimization of the detector spatial resolution, the minimization of the thermal load and the long-term damage resulting from high radiation doses. Four segmented dumps are currently used in the CTF3 complex. Their measured performance and limitations are presented in this paper. Typical beam spectra as measured in the CTF3 linac are also presented along with a description of the RF manipulations needed for tuning the beam energy spectrum.
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| 10. |
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